IMED2004 Study Guide - Final Guide: Hh Blood Group, Fucose, Epistasis
Document Summary
Can only add a or b if have substrate h. So, expression of abo locus alleles depends on genotype at the h locus. Most people have the dominant h allele. The abo locus alleles are hypostatic to the recessive h allele. Hence blood type o can be via h_ii. (no h to add the sugar to). This is a common theme in epistasis. A gene (e. g. h) that affects an early step in a pathway is epistatic to genes affecting subsequent steps (ia & ib). Effects of genes of a later step depend on product of earlier reaction. Influences the expression of the i locus gene product. Only see full expression of i if h is present. It is epistatic over hypostatic abo locus, and don"t have fucose. Only see full expression of big i when we have big h present. Different rearrangements & point mutations in mtdna cause human disease.
